For surfactants and surface treatment agents with fluorochemical chains, longer perfluoroalkyl chains contain a higher percentage of fluorine at a given concentration and typically provide better performance. However, the fluorinated materials derived from longer perfluoroalkyl chains are more expensive. Reduction of the fluorine content with delivery of the same or higher performance is therefore desirable. Reducing the fluorine content would reduce the cost, but it is necessary to maintain product performance.
Desimone et al., in WO 02/26921, described hybrid phosphates of the structure RfO—PO(ORH)(O−M+) wherein Rf is CnF(2n+1)(CH2)m, RH is CnH(2n+1), or CnF(2n+1))(CH2)m, n and m are 1 to 24, and M+ is K+, Na+, or NH4+. Desimone et al. described the use of these compounds as surfactants for use in liquid carbon dioxide, but not as surfactants in water or other media.
It is desirable to improve surfactant performance, in particular lowering of surface tension in aqueous systems, and to increase the fluorine efficiency, i.e., boost the efficiency or performance of the surfactants so a lower proportion of the expensive fluorine component is required to achieve the same level of performance, or to have better performance using the same level of fluorine. Especially desirable would be surfactants having similar or superior performance in aqueous systems compared to current commercial products but having shorter perfluoroalkyl groups. The present invention provides such surfactants.